Apparatus for bending steel bars to form concrete reinforcement elements

ABSTRACT

Apparatus for bending steel bars to form concrete reinforcement elements, having a device (3, 4; 18) for feeding bars to a transfer device (8), by means of which in each case one group of bars can be inserted in two bending frames or stations, (2, 2&#39;), each having members (11, 12) for bending the bars in transverse direction the transfer device having at least one pair of operation-controlled gripper tongs (10) which can be swivelled from a first position, in which they receive a plurality of bars from the bar feed device, and clamp the bars, into a second position, in which they insert the bars into the gap between the bending members.

FIELD OF THE INVENTION

The invention relates to an apparatus for bending steel bars to formconcrete reinforcement elements, having a device for feeding bars to atransfer device, by means of which in each case one group of bars can beinserted between bending members in the transverse direction of the bars

BACKGROUND

In an apparatus of this type known from German Patent 3,010,923, barscompiled in groups by means of stops are fed successively on a slopingplane to the transfer device which feeds the groups of bars lyingvertically above one another on a roller runway to a downstream tyingdevice for tying off the group and to a bending machine, in which thegroup is bent into the desired shape. The main disadvantage of thisapparatus consists in the fact that the groups of bars are passedwithout guiding to the transfer device. The transfer device has aplurality of rows of vertically disposed pairs of rollers; this can leadto malfunctions and misalignment of the bars. It is additionallydisadvantageous in the known design that the groups of bars firstly haveto be wrapped with tapes or wire or bonded to one another by welding sothat they can subsequently be fed to the bending device in thelongitudinal direction.

German Patent 3,644,482 discloses an apparatus for processing steelbars, having a tool, e.g. a bending slide, in which apparatus in eachcase a plurality of bars is transported both towards the bending slideand, after processing, away from the slide transversely to thelongitudinal direction by means of arms which are mounted on both sidesof the tool and can be swivelled as a unit. In this construction, thebars must be placed manually on the swivel arms. It is furthermoredisadvantageous that the bars are not fixed on the swivel arms and,during swivelling of the arms, are held only by one step in therespective swivel arm. A further disadvantage emerges in the fact thatthe bars to be bent are placed on inclined, ramp-shaped elements and,after the lowering of the swivel arms, slide into an operating channelof the bending device only due to the force of gravity transversely tothe longitudinal direction In this process, as a result of thesimultaneous feeding of a plurality of bars, a mutual hindrance can takeplace during sliding, in particular if the bars are long and ribbed,thereby making a defined, orderly arrangement in the operating channelmore difficult.

THE INVENTION

It is an object to provide an apparatus which avoids the disadvantagesof the known apparatus and guarantees a reliable, simultaneous transferof a group of bars from the feed device to the bending device. At thesame time, the apparatus is intended to allow the satisfactoryprocessing of bar material present in different shapes.

Briefly, according to the invention, the transfer device has at leastone pair of operation-controlled gripper tongs which can be swivelledfrom a receiving position, in which they receive a plurality of barsfrom the bar feed device and clamp said bars, into an insertionposition, in which they insert the bars into the gap between the bendingmembers.

With this construction, a reliable reception of a group of bars isachieved which is held fixedly until it is placed between the bendingmembers and, if appropriate, also during the bending operation so thatthe bars cannot change their mutual relative position.

In accordance with a preferred embodiment of the invention, the grippertongs are arranged at the end of a swivel arm which is adjustable in acontrolled telescopic manner. In this case, the jaws of the grippertongs are expediently mounted so as to be jointly swivellable on theswivel arm in the form of a gripper tong head. By this means, theprecision of the reception and transfer of the bars is improved.

The swivel arm is advantageously mounted so as to be swivellable on aframe bearing the bending members.

In one design of the invention, in the region of the receiving positionof the gripper tongs, the frame has a buffer surface for bars fed by thebar feed device in the transverse direction of the bars, an alignmentdevice being assigned to the buffer surface for mutual alignment of theone end of the bars. In this case, above the buffer surface, the barfeed device advantageously has a bar discharge device, by means of whichbars can be fed individually in succession to the buffer surface.

In accordance with an alternative embodiment of the apparatus, the barfeed device has parallel, continuous, circulating conveyor units,between which the gripper tongs engage in their receiving position. Inthis case, a discharge device for the bars is advantageously arrangedabove the run-in end of the conveyor units, which discharge device hasat least one swivel channel for discharging one bar in each case, adistributor flap or the like preferably being provided between thedischarge device and the conveyor units for passing the bar to theconveyor units or away from the latter.

According to another feature of the invention, two frames are provided,which are adjustable relative to each other with mutual spacing in thelongitudinal direction of the bars and which are each fitted withbending members and, on their inside, with swivel arms bearing grippertongs, a common bar feed device and a common bar alignment device beingassigned to the frames.

Furthermore, according to the invention in this embodiment one of thepairs of gripper tongs for clamping the bars can be actuated during thebending operation and/or during the adjustment of the frames.

In accordance with a development of the invention, provision is made forthe transfer device to have a separate operating device for each pair ofgripper tongs, each pair of gripper tongs, in turn, being fitted with aseparate operating device for the controlled opening and closing of saidgripper tongs. By this means, a reliable guiding and transfer of thebars is guaranteed during all phases of operation of the apparatus.

THE INVENTION

The invention is described in greater detail below by way of exemplaryembodiments with reference to the drawings, in which:

FIG. 1 shows diagrammatically a perspective view of an apparatusaccording to the invention,

FIG. 2 shows diagrammatically a section of a further exemplaryembodiment of the invention and

FIG. 3 shows a view of a detail of another embodiment of the apparatus.

DETAILED DESCRIPTION

The bending apparatus 1 illustrated in FIG. 1 has two bending frames 2,2', arranged spaced apart, for the simultaneous bending of a pluralityof rods S. Provided above the bending apparatus 1 is a bar feed deviceand a bar feeding device 3. Rods S are fed individually by a lateralfeed device 4 in the direction of the arrow P₁, i.e. in the longitudinaldirection of the bars. The diagrammatically illustrated feed device 4 issuitable for feeding aligned, straight bars in standard lengths and isfitted with advancing rollers, a length measuring device and a pair ofshears (not illustrated). A levelling device can be arranged upstream ofthe feed device 4 so that bar material coming from drums or reels canalso be processed. If the bar material is already available in therequired, ultimate finished length, the length measuring device and theshears are not required or are not in operation.

The bar feed device 3 has at least one discharge channel 5 arranged soas to be swivellable. After the swivelling of the discharge channel 5,the bar S drops in the direction of the arrow P₃ onto an inclined bufferand guide surface 7, e.g. formed by a plate on the upper side of thebending frames 2, 2' and rolls into a bar gripping and transfer device 8which is in the receiving position for a plurality of bars and has twoswivel arms 9 and associated gripper tongs 10.

Each swivel arm 9 is mounted so as to be swivellable on the inside ofone of the bending frames 2 or 2' and can be swivelled corresponding tothe arrow P₄ from the bar receiving position into a bending position.The bending position is defined by the location of a bending head 13 or13' consisting of bending mandrel 11 and bending bolt 12, which bendinghead is expediently mounted in each of the bending frames 2 or 2' so asto be lowerable and operable in a controlled manner. In an alternativeembodiment, solely the bending bolt 12 is lowerable.

Each swivel arm 9 is divided into two parts and is adjustable in heighttelescopically with its upper part bearing the gripper tong head 10 inrelation to the lower part mounted on the bending frame corresponding tothe double arrow P₅ in order to be able to bring the bars into thebending position between bending mandrel 11 and bending bolt 12 of thebending head 13. The gripper tongs 10 are attached so as to beswivellable on the upper part of the swivel arm 9 corresponding to thedouble arrow P₆ in order to be able to be positioned precisely in thereceiving position and in order to be able to precisely pass the bars Sto the bending heads 13, 13' of the bending frames 2, 2'. The grippertongs 10 (see also FIG. 2) are formed by a lower jaw 14' and upper jaw14" which is swivellable corresponding to the double arrow P₇, whichjaws are capable of holding the bars S fixedly during the swivelmovement P₄ of the swivel arm 9 from the receiving position into thebending position and also during bending. Furthermore, the bars S, whichare held fixedly by the jaws 14', 14", can be lifted out of the bendingposition with the aid of the swivel arms 9 during the change in positionof the bending tools required for reversing the bending direction to theextent that a lowering of the bending head or of one of the bendingtools is not required for the change in position. Rather, the grippertongs are actuated accordingly for transferring the bars from one sideof the central bending mandrel 11 to the other side of the latter.Additionally, before carrying out the swivel movement P₄ of the swivelarm 9, the gripping jaw 14" can be folded back into the receivingposition to such an extent that the jaw 14" does not collide with thebars in the bending heads 13, 13'.

The bending heads 13, 13' bearing the bending members 11, 12 arearranged so as to be displaceable corresponding to the double arrow P₂₁(FIG. 1), i.e. in the longitudinal direction of the bars into therespective bending frames 2 or 2'. By this arrangement, the bendingmembers 11, 12 are each displaceable relative to the gripper tongs 10 sothat the bending of a reference arc with a radius greater than theradius of curvature of the central bending mandrel 11 is possible bydividing the overall bending process into a plurality of of successivepartial bending steps. In this case, the reference arc is divided into aplurality of partial sections and the overall bending angle into aplurality of partial bending angles. A stepwise displacement of thebending members 11, 12 relative to the gripper tongs 10 clamping the barmaterial is obtained alternating with a partial bending around thepartial bending angle corresponding to the length of the partialsections until the desired reference arc has been completed.

OPERATION

After the gripper tongs 10 have been filled with a predetermined numberof bars S, the bars S are fixed with the aid of the jaw 14". Before theyare fastened in the gripper tongs 10, the bars S are aligned against astationary stop 15" with the aid of an extendable alignment device 15which is arranged on a stationary component (not shown). For thispurpose, the alignment device 15 is provided with a stop part 15'displaceable corresponding to the double arrow P₈. The bending frames 2,2' of the bending apparatus 1 are displaceable corresponding to thedouble arrow P₉ on rails 16, which are indicated only diagrammatically,in order to be able to bend the bars at different bending pointscorresponding to the reinforcement rods or stirrups to be produced.During the adjustment of the bending frames, the bars are held fixedlyby means of the gripper tongs 10 of one of the frames. The tongs 10associated with the other frame are slightly opened for guiding the barsarranged above one another during the adjustment of the frames. Theslight opening of the tongs allows the bars to glide in the slightlyopened gripping jaws 14', 14" gripping jaws 14', 14" without changingthe arrangement of the bars.

For reliable support of rods or stirrups with large bent-over limbs, aresting plate 17" is provided on the bending frames 2, 2', in additionto the resting surfaces 17 and 17'. The stationary resting plate 17"also serves as a covering plate for the bar feed device 3. The restingplate 17" can also be of two-part construction, in which case each partis connected to a bending frame 2 or 2' and is displaceable with thelatter.

As is shown in the exemplary embodiment illustrated in FIG. 1, it isalso possible within the framework of the invention to feed bars S intheir transverse direction, preferably horizontally, to the buffer andguide surface 7 and thus to the bar gripping and transfer device 8 withthe aid of an additional bar feed device (FIG. 2) arranged on the rearside of the bending apparatus 1. That bar feed device 18, as shown inFIG. 2, suitably consists of one or more parallel continuous conveyorbelts 19 which are guided at one end around rollers 21 rotating in thedirection of arrow P₁₁ and are driven by means of a suitable device (notshown).

FIG. 2 also shows a further exemplary embodiment of an apparatusaccording to the invention. In this apparatus, the bars S are fed to adropping and distributor device 22, which corresponds essentially to thedropping device 3 in accordance with FIG. 1, via a feed device 4 inaccordance with FIG. 1 which can be loaded, as in the exemplaryembodiment according to FIG. 1, with different shapes of bar material.The bar discharge device 22 has at least one swivellable dischargechannel 5' which is arranged on a channel bearer 6' and can be swivelledcorresponding to the double arrow P₂. Below the bar discharge, ordropping and distributor device 22 there is an adjoining discharge duct24 provided with lateral guide plates 23 extending in the longitudinaldirection of the bars, which discharge duct passes the bars S in thedirection of the arrows P₃ to a distributor flap 25 which can beswivelled corresponding to the double arrow P₁₂. Depending on theposition of the distributor flap 25, the bars S can either be passed tothe bar feed device 18 by an inclined conductor plate 26, arranged abovethe bar feed device 18, which is constructed in form of circulatingunits. The bars drop in the direction of the arrow P₁₃ or,alternatively, forwarded to an unloading and intermediate magazine via afurther, likewise inclined conductor plate 27, facing away from the barfeed device 18, in the direction of the arrow P₁₄. This form of thedropping and distributor device 22 is particularly advantageous forseparating non-utilisable remnant lengths and is conceived, inparticular, for the case that the higher operating speed of the droppingand distributor device 22 in relation to the relatively slow productionspeed of the bending device is to be fully exploited in order to providefor continuous operation.

The bars S are conveyed with the aid of the bar feed device 18 in thedirection of the arrow P₁₀ into the gripper tongs 10 of the transferdevice 8 which engage in their first position between the parallel,continuously circulating conveyor units of the bar feed device. Afterthe gripper tongs 10 have been filled with the number of bars to bebent, the jaws 14" close, if appropriate only after the alignment device15, not illustrated in FIG. 2, has aligned the bars at the ends, and theswivel arms 9 swivel from the receiving position into the bendingposition.

In order to allow the bars S to be positioned between the bendingmandrel 11 and the bending bolt 12, it is possible, as illustrated inthe exemplary embodiment according to FIG. 2, either to displace theupper part of the swivel arm 9 in its height corresponding to the doublearrow P₅ or to lower the entire bending head 13 by a suitable loweringmechanism 42, shown only schematically, or even only the bending bolt 12corresponding to the double arrow P₁₅. Bending bolt 12 can be lowered bya suitable lowering mechanism 43, shown only schematically. A restingplate 17'" which serves for supporting stirrups with long limb lengthsand can be constructed in a stationary manner and for both frames 2, 2'jointly or in two parts connected to the frames. It is illustrated onlydiagrammatically.

The drive and operating elements necessary for the movement of theindividual devices are constructed in a known manner and have beenomitted in FIGS. 1 and 2 for the sake of clarity shown onlyschematically.

In the embodiment illustrated in FIG. 2, the gripper jaws, instead ofengaging in the receiving position between parallel conveyor elements ofthe bar feed device 18 could also be arranged before the run-off end orbelow the run-off end of the conveyor units or unit, if a singlecontinuously circulating conveyor member is used.

An alternative embodiment of the bar gripping and transfer device 8'(see FIG. 3) has two pairs of gripper tongs 28 which are eachconstructed as shown in FIG. 3, in which a view of the inside of thebending frame 2 is shown. The gripper tongs 28 have an angled clampingarm 29 and a likewise angled clamping lever 30 which is formed by ashort lever arm 30' and a long lever arm 30". The clamping arm 29 ismounted at one end on a pivot joint. The clamping lever 30 is pivotablymounted at its angled point on the joint. The joint is formed by aneccentrically arranged bearing pin 31 of an eccentric crank 32 indicatedonly by dashed lines. Mounted on the clamping arm 29 as drive device isa hydraulically operable operating piston-cylinder unit 33, the pistonrod 34 of which is linked to the short lever arm 30' of the clampinglever 30.

By operation of the drive device 33, the piston rod 34 executes a linearmovement corresponding to the double arrow P₁₆ so that the clampinglever 30 is swivelled relative to the clamping arm 29 corresponding tothe double arrow P₁₇, so that the bars S are clamped between clampingjaws 35 at the free end of the clamping arm 29 and of the lever arm 30".

The clamping jaws 35, which are parallel to each other in the closedposition, consist of resilient material which is as resistant to wear aspossible so that a plurality of bars S can be clamped securely even inthe case of the position of the clamping jaws not being completelyparallel and in the case of deviations in the diameter of the individualbars.

The eccentric crank 32 forming the swivel arm for the gripper tongs ismounted with its swivel axis 36, which lies on the axis X--X of thecentral bending mandrel 11, on the inside of the respective bendingframe 2 or 2' and executes a swivel movement corresponding to the doublearrow P₁₈ (FIG. 3) under the effect of a drive device (not illustrated).In addition, a swivel arm 37 is mounted concentrically to the swivelaxis 36 of the eccentric crank 32 so as to be swivellable on the insideof the respective bending frame 2 or 2', which swivel arm executes aswivel movement corresponding to the double arrow P₁₉ under the effectof a further drive device (likewise not illustrated). In this case, thebearing of the swivel arm 37 can be formed, for example, by a hollowshaft (not illustrated), in which the eccentric crank 32, in turn, ismounted concentrically.

The free end of the swivel arm 37 is coupled to the clamping arm 29 viaa connection strap 38, the attachment point being located as near aspossible to the free end of the clamping arm 29. The connection strap 38effects a forced coupling of the movements of the clamping arm 29 and ofthe clamping lever 30.

Operation, embodiment of FIG. 3: The bars S pass via a buffer and guidesurface 7, constructed corresponding to the exemplary embodimentaccording to FIG. 1, into a collection device 39 which is indicated onlydiagrammatically and is arranged on a stationary component (not shown)of the apparatus. The collection device 39 preferably has U-shaped crosssection and a depth such that all the bars to be bent simultaneously arearranged above one another in the correct position and can be picked upby the gripper tongs 28. For adapting the collection device 39 todifferent diameters of the bars to be bent, a side wall 40 of thecollection device 39 can, if appropriate, be constructed so that it canbe displaced in parallel relative to the opposite side wall, asillustrated by double arrow P₂₂, by a suitable mechanism, shown onlyschematically at 44.

For taking over the bars from the collection device 39, the grippertongs 28 are swivelled into the receiving position defined by thecollection device 39 by operating the eccentric crank 32 and the swivelarm 37 corresponding to the double arrow P₂₀. By operating the drivedevice 33, the clamping lever 30 swivels towards the clamping arm 29corresponding to the double arrow P₁₇ so that all the bars are clampedsecurely between the clamping jaws 35. Before the bars are fastened inthe gripper tongs 28, if appropriate, the bars are aligned at their endsby means of an alignment device described with reference to FIG. 1 (notillustrated in FIG. 3).

By further operation of the eccentric crank 32 and the swivel arm 37,the bars, now clamped between clamping arm 29 and clamping lever 30,pass into the bending position between the bending members 11, 12,arranged on the bending base 13.

During the adjustment of the bending frame or bending frames 2 or 2',the bars are held fast by means of the gripper tongs 28 of one of thebending frames, whereas the gripper tongs 28 of the other bending frameare opened slightly for guiding the bars lying above one another inorder to allow the bars to glide between the clamping jaws 35 withoutchanging the bar arrangement.

Alternatively it is also possible within the scope of the invention toopen the gripper tongs 28 of the other bending frame mentioned abovecompletely and to guide the bars only through the bending members 11, 12which form a suitably narrow guide gap.

In order to be able to carry out a reversal of the bending direction inthe exemplary embodiment of an apparatus according to the inventiondescribed with reference to FIG. 3, the eccentric crank 32 is operatedand the swivel arm 37 is swivelled in such a way that the clamping armis jointly lifted corresponding to the double arrow P₅. The bars 29,held by the closed gripper tongs 28, and the clamping lever 30 are thuslifted out of the bending position, and are subsequently transferred byjoint swivelling of the clamping arm 29 and the clamping lever 30corresponding to the double arrow P₂₀ from one side of the centralbending mandrel 11 to the other side of the latter and finally, afterthe change in position of the bending bolt 12 has been completed, arelowered into the new bending position by joint lowering of the clampingarm 29 and the clamping lever 30 corresponding to the double arrow P₅.The eccentric crank 32 and the swivel arm 37 are matched to each otherin their sequences of movement in such a way that, during the transfermovements, the bars lying above one another remain aligned, and alwaysparallel to the central bending mandrel 11.

After completion of all the bending operations, the eccentric crank 32and the swivel arm 37 are again operated so that the bars are lifted outof the bending position with the gripper tongs 28 closed by jointlifting of the clamping arm 29 and the clamping lever 30 correspondingto the double arrow P₅. Subsequently, the bars are swivelled out of theregion of the resting surface 17 of the bending frame 2 by jointswivelling of the clamping arm 29 and the clamping lever 30corresponding to the double arrow P₂₀ and are finally placed with theaid of the clamping drive device 33 on a preferably inclined run-offplate 41 by joint lowering of the clamping arm 29 and the clamping lever30 and after the gripper tongs 28 have been opened.

The bar gripping and transfer device 8' in accordance with FIG. 3 andthe collection device described can also be used in the embodimentillustrated in FIG. 2.

In order to be able to carry out a reversal of the bending direction inthe apparatus according to FIGS. 1 and 2, as in the exemplary embodimentaccording to FIG. 3, the swivel arms 9 and the gripper tongs 10 areactuated for transferring the bars from one side of the central bendingmandrel 11 to the other side of the latter. Furthermore, these swivelarms and gripper tongs are actuated for lifting out and discharging thebars after completion of all the bending operations.

A control device (not illustrated) is provided for controlling theactuable, movable devices and for matching the movements of thesedevices to one another and for controlling and monitoring the bartransport from the feed devices into the bending device, in particularfor individual controlling of the swivel arms and the gripper tongs andfor carrying out the required bending processes on the bars, by means ofwhich control device the drive and operating elements are controlled.

It is understood that the invention is not restricted to the exemplaryembodiments illustrated; on the contrary, these can be modified invarious ways within the framework of the general concept of theinvention. In particular, in the exemplary embodiment shown, more thantwo swivel arms with gripper tongs could be provided which operatealternately in order to allow a continuous operation.

The bar feed device 3, 4 of FIG. 1 as well as the bar feed device 18 ofFIG. 2 are preferably both installed to permit selective use and, incase of a feeding difficulty in one of them, to provide for an alternatefeed of bars to the apparatus.

We claim:
 1. Apparatus for bending a plurality of steel bars to formconcrete reinforcement elements or stirrups,said apparatus defining alongitudinal direction parallel to a longitudinal direction of the bars,said apparatus having a bar feed device; two bending frame means (2,2'), each bending frame means including bending members (11, 12) spacedfrom each other and defining a bar gap; means for adjustably mountingsaid bending frame means for adjustment relative to each other in alongitudinal direction of the apparatus, and comprising a bar grippingand transfer device (8, 8') coupled to each of the bending frame means(2, 2'),the bar gripping and transfer devices each having gripper tongs(10, 28) and conjointly movable gripping jaws (14', 14"), said grippertongs being movable between a receiving position for receiving andclamping a plurality of bars between the gripping jaws (14', 14"), and adischarge position for placing said plurality of bars clamped in thegripping jaws in the bar gap of the bending members (11, 12); a bufferand guide surface (7) positioned transversely with respect to thelongitudinal direction of the apparatus and located in the vicinity ofthe receiving position of the gripper tongs (10, 28), said buffer andguide surface (7) receiving the bars from the bar feed device (3, 4;28); and a common bar alignment device (15) operatively associated withthe buffer and guide surface (7) for aligning at least one of the endsof the bars with respect to a reference so that said bars can be placedwithin the gripper jaws (14', 14") at the receiving position when inalignment.
 2. The apparatus of claim 1, wherein said movable grippertongs (10, 28) include an adjustable swivel arm for pivotably mountingthe respective gripping tongs (10, 28) on the associated bending framemeans (2, 2').
 3. The apparatus of claim 2, wherein said gripping jaws(14', 14") of said gripper tongs define a gripping head (10), saidgripping head being pivotably mounted on said swivel arm (9) for jointmovement of the gripping jaws (14', 14").
 4. The apparatus of claim 1,wherein said common buffer and guide surface (7) is positioned adjacentsaid bar feed device (3) to receive the plurality of feed bars adjacenteach other.
 5. The apparatus of claim 1, wherein said bar feed device(18) includes at least two parallel continuously circulating conveyorelements (19); andwherein the gripper tongs (10), when in the receivingposition, engage between two of said parallel continuously circulatingconveyor elements.
 6. The apparatus of claim 5, wherein the bar feeddevice (18) further includes a dropping and distributor device (22)having an exit channel (24);swivel means (5', 6') positioned to receivesaid bars from the bar feeding device, and individually feeding saidbars to said exit channel (24); and a distributor flap (25) locatedbeneath the exit channel and directing a bar (S), respectively, to saidconveyor elements (19) or to a discharge chute (27) away from thebending frames (2, 2').
 7. The apparatus of claim 1, including controlmeans (30', 31, 32, 33, 34, 37, 38; P₆, P₇) coupled to the gripper jaws(14', 14"; 35) for clamping the bars (S) and controlling said clampingduring at least one of:bending operation of said bending members of thebending frame means; adjustment of said bending frame mans (2, 2')relative to each other in the longitudinal direction of the apparatus(1).
 8. The apparatus of claim 1, wherein said bending members (11, 12)are coupled to form a bending head (13, 13'); andwherein said bendinghead (13, 13') is movable in the respective bending frame means (2, 2')from the receiving position to the discharge position of the bendinghead to permit insertion of said rods (S) between the bending members(11, 12) of the respective head (13, 13'), when the gripper tongs aremoved into the discharge position, and simultaneous bending of aplurality of bars.
 9. The apparatus of claim 1, wherein the bendingmembers (11, 12) of each bending frame means (2, 2') are located on arespective bending head (13, 13');and wherein the bending head isslidable in the respective bending frame means in the longitudinaldirection.
 10. The apparatus of claim 1, further including an engagementor resting surface (17) operatively associated with each bending framemeans (2, 2'), said rest surface having at least a portion (17", 17'")located above the moving range of said gripper tongs when the grippertongs are in an extreme position,said rest surface supporting bent limbsof the bars after the bending members have bent the bars.
 11. Theapparatus of claim 1, wherein each one of the gripper tongs (28)includes a clamping arm (29) and a clamping lever (30), said clampinglever being pivotable towards and away from said clamping arm;a bearingpin (31) pivotably coupling said clamping arm (29) and said clampinglever (30) together; drive means (33, 34) engageable with both saidclamping arm (29) and said clamping lever (30) for relative pivotingmovement of said clamping arm and clamping lever towards and away fromeach other; and means for controlling the movement of said clamping arm(29) and clamping lever (30) forming said tongs comprising an eccentriccrank (32) secured in the respective bending frame means (2, 2') andoperable for moving the respective tongs between the receiving positionand the insertion position, said eccentric crank retaining the bearingpin; a separately drivable swivel arm (37) mounted concentrically tosaid eccentric crank on the respective bending frame means; and couplingstrap means (38) connecting the swivel arm (37) to the clamping arm(29).
 12. The apparatus of claim 1, wherein said bending members (11,12) define a central bending mandrel (11) and a bending bolt (12) spacedfrom said bending mandrel;and wherein said gripper tongs (10, 28) aremovable to a discharge position on either side of said mandrel (11),with respect to movement of the respective gripper tongs between saidreceiving and discharge position.
 13. The apparatus of claim 1, whereinthe gripper jaws (14', 14"; 35) of one of said gripper tongs arecontrollable for slight release of gripping pressure to permit guidingof a plurality of bars (S) in the jaws upon adjustment of position ofone of the bending frame means (2, 2').
 14. The apparatus of claim 1,wherein said gripper tongs (10, 28) are additionally movable to anejection position, said tongs gripping the bars, after completion of abending operation, in the discharge position, and moving said then bentbars into the ejection position;and ejection guide mean (41) areprovided for receiving the bent bars from the ejection position, saidtongs opening the gripper jaws when in the ejection position to permitrelease of the bent bars.
 15. The apparatus of claim 1, furtherincluding a bar collection device (39) for receiving a plurality of barsfrom said buffer and guide surface (7);and wherein the gripping jaws(14, 14'; 35) receive the bars from said collection device when in thereceiving position.
 16. The apparatus of claim 15, wherein thecollection device, in cross section, defines an essentially U-shapedchannel having a pair of opposed side walls;and wherein at least one ofsaid side walls (40) is movable towards and away from the other toprovide for adjustment in accordance with the thickness of the bars (S)collected in said collection device.
 17. The apparatus of claim 1,wherein said common bar alignment device (15) comprises a stationarystop (15") and a displaceable stop (15').